Recently, increasingly stringent demands for performance have been placed on a memory system that uses a NAND type flash memory (hereinafter referred to as a NAND memory) as a nonvolatile memory, for example, a solid state drive (SSD) system. For higher performance without a cost increase, the development of a NAND controller that makes the most use of the NAND memory will be more important.
Meanwhile, a NAND package (including the NAND memory) used in an SSD generally includes a plurality of NAND chips to hold down the number of external pins and to enhance performance and capacity. In the SSD of this type, a plurality of NAND memories need to be more efficiently used.